Lymphocyte—Epithelial Cross-Talk in the Intestine: Do Nonclassical Class I Molecules Have a Big Part in the Dialogue?

Publisher Summary This chapter focuses on the behavior and properties of nonclassical class I molecules expressed by mouse intestinal epithelial cells, and the possible role these molecules may have in the development and function of mouse intestinal intraepithelial lymphocytes (IEL). IEL have a phenotype that is distinct from other T-cell populations, and these lymphocytes may be the product of a separate, thymus-independent lineage. If such a lineage exists, it would be likely that the intestinal epithelium plays a major role in its development. It is also possible, however, that some IEL are derived from thymus-derived T cells. This is evidenced by the ability of conventional CD4 + cells to home to the gut epithelium in scid mice, and to acquire characteristics of the T cells that normally reside in the intestine. This chapter shows that nonpolymorphic class I molecules expressed in the intestine have unique properties, most notably, their lack of a requirement for TAP in order to be expressed on the cell surface. This lack of a TAP requirement may provide some insight into the specialized function of the TL antigen and mCDl in the mucosal immune system. This chapter further demonstrates that mCDl can function as an antigen-presenting molecule, and that it presents peptide antigens distinct from those presented by classical class I molecules.